Dark Energy Survey(DES) Exposes a Infrequent Superluminous Supernova

The first pictures taken by
the Dark Energy Survey (DES) after the study initiated in August 2013 have exposed
a rare, 'superluminous' supernova that exploded in a galaxy 7.8 billion light
years away. The stellar eruption, so-called DES13S2cmm, simply outshines maximum
galaxies in the Cosmos and might still be seen in the data six months later, at
the end of the first of what will be five years of spotting by DES. The occurrence
was discovered by Andreas Papadopoulos, a postgrad student from the University of
Portsmouth, who presented the finding at the National Astronomy Meeting 2014 in
Portsmouth on Wednesday, 25 June. Superluminous supernovae are a new discovery,
only being accepted as a separate class of objects in the past 5 years. These
cosmic eruptions are 10-50 times perkier at their peak than the brightest standard
kind of supernovae and, unlike other supernovae; their explosive reasons remain
anonymous. Papadopoulos said "Fewer than forty such supernovae have ever
been found and I never expected to find one in the first DES images! As they
are rare, each new discovery brings the potential for greater understanding --
or more surprises."

Artist's impression of a Magnetar Credit: ESO/L.Calçada

It turns out that even in
this rare group, DES13S2cmm is strange and unfamiliar. The rate that it is diminishing
away over time is considerably slower than for maximum other superluminous
supernovae that have been detected so far. This alteration in brightness over
time, or 'light curve', provides data on the procedures that triggered the
explosion and the configuration of the material emitted.

Before (left) and after (center) images of the region where DES13S2cmm was detected. On the right is a subtraction of these two images, displaying a bright new object at the center — a supernova. Credit: Dark Energy Survey.

Dr Mark Sullivan of
Southampton University ran the program to achieve spectroscopy of DES13S2cmm by means of the Very Large Telescope at
Cerro Paranal, Chile. Sullivan said "It’s unusual, slow decline was not
apparent at first, but as more data came in and the supernova stopped getting
fainter, we would look at the light curve and ask ourselves, 'what is this?” Understanding
the backgrounds of DES13S2cmm is very
difficult. Radioactive decay is acknowledged to power usual supernovae, but not
from such great quantities of material. Dr Chris D'Andrea of the University of
Portsmouth, co-author on this research, explains "We have tried to explain
the supernova as a result of the decay of the radioactive isotope Nickel-56, but
to match the peak brightness, the explosion would need to produce more than
three times the mass of our Sun of the element. And even then the behavior of
the light curve doesn't match up." The group is now studying unconventional
descriptions, counting that DES13S2cmm
is a standard supernova that has formed at its core a magnetar, a mysterious
neutron star rotating hundreds of times per second, generating a magnetic field
a trillion times sturdier than that on Earth. Energy from the magnetar is then inserted
into the supernova, creating the eruption extremely bright. D'Andrea noted "Neither
model is a particularly compelling match to the data,"

With DES opening its second term
in August, the search is on for further superluminous supernovae.